1. Field of the Invention
This invention relate; to a head mounted display (hereinafter referred to as "HMD") for watching images projected from a display and for listening to sound by putting it on the head, and also related to an image display system which utilizes the HMD.
2. Description of the Prior Art
The HMD has been used as a device for watching images projected from a display device placed on the front side of the HMD by putting it on the head. The display device provided in the HMD usually comprises liquid-crystal panels which display desirable images at positions respectively close to a right eye and a left eye. In this display device, the liquid-crystal panels are inclined against the eyes to artificially set the angle formed by the lines of eight (hereinafter referred to as "convergence angle"). Hence the display device is capable of forming the same images as those formed when fixing the eyes on a position 1 to 2 meters away. Moreover, a predetermined angle of visual field (angle of horizontal view) can be formed by supplying the images of the liquid-crystal panels through lenses. Images projected from the right and left liquid-crystal panels are synthesized to form a binocular image, thereby enabling the reproduction of wide-angle images with an enlarged angle of visual field and of three-dimensional images.
This HMD can be used in various fields, for example, in order to play games In three-dimensional space (virtual space) or to simulate, for example, the interior of a building in a three-dimensional mode.
One example of this type of HMD is one with the above-described display device supported by a head band which is fastened to the head of a player, that is, a user, thereby securing the display device on the head.
As another example, there is an HMD with a slide-type frame, length of which is adjusted to definitely secure the display device on the head This slide-type HMD comprises, for example, a front frame with a display device on its front side, and a back frame which is assembled with the front frame in a slidable manner. Bands with racks are provided at both ends of the front frame. These bands are introduced into the back frame, and a pinion which engages the racks is inserted into and set at the above-mentioned racks. By turning this pinion, the distance between the front frame and the back frame is adjusted, thereby enabling the attachment and detachment of the HMD to and from the head.
With this type of HMD, it is necessary to adjust the positions of the right and left liquid-crystal panels according to the distance between a player's eyes in order to obtain good images. It is also necessary to adjust the angle formed by the optical axes of the liquid-crystal panels in accordance with the type and content of images in order to obtain predetermined wide-angle images and three-dimensional images.
In conventional HMD's, the positions of the liquid-crystal panels are fixed in a general manner. Even if the positions or the liquid-crystal panels can be adjusted, it is only possible to do so by manual operations. Therefore, it is difficult to adjust the positions or the liquid-crystal panels quickly and accurately according to the distance between the eyes for each player.
There is also a similar problem with regard to adjustment of the angle formed by the optical axes of the liquid-crystal panels when a player is watching a reproduced screen. It is difficult to switch images from one to another as appropriate and in real time, among three-dimensional images, wide images, and combined images of these two kinds, in accordance with the type and content of the images.
When playing a game with this HMD, the player sometimes moves his/her head fiercely depending on the content of the game. With the HMD which is constructed so as to fasten the above-mentioned bands to the head, it is difficult to sufficiently support the display, which is a heavy material, with the head bands, resulting in problems such that the head bands bend or the HMD slips off the head. Accordingly, there are some problems in that the HMD drops off the head during the game, the HMD cannot stay at its original position on the head, and the comfort while wearing the HMD on the head decreases.
On the other hand, if the HMD is constructed so as to fasten the above-described frames to the head, the frame portions are rigid compared to the aforementioned HMD which utilizes the head bands and, therefore, there is no problem like the bending of the frames. However, there is a problem that a user cannot feel satisfactorily comfortable when wearing the HMD. Moreover, there is another problem in that the HMD drops off the head if the player moves her head fiercely when using the HMD, and the HMD hardly stays at a certain position when it is put on the head.
With the HMD constructed so as to fasten the frames to the head, in order to take the HMD off the head, it is necessary to turn the handle provided on the pinion fully to expand the distance between the front frame and the back frame so that the HMD can be completely taken off the head. Accordingly, there is a problem that it is difficult to put on the HMD and take it off the head. Moreover, since the handle is mounted on the back side of the head in this HMD, it is hard to operate the handle.
Furthermore, HMD's at amusement parks, game centers, etc. are used by many and unspecified players. Conventional HMD's are generally constructed in a manner such that a player's eye regions touch the lens surfaces, etc. as in the case of a binocular with eye cups. The speaker portions of headphones are generally constructed in a manner such that, for example, earphones are inserted into the ears, just like speaker portions used for audio equipment, so that the speaker portions touch the player's ears directly. Accordingly, there is a problem that such constructions in direct contact with the eyes, ears and other body parts of many and unspecified people are not preferable for sanitary reasons.
This invention aims to solve the above-described problems of the prior art. An objective of the invention is to provide an HMD which has a display device capable of being secured on the head with certainty, which realizes fully improved comfort when it is put on the head, and which can certainly maintain an optimal position while wearing, even if the head is moved fiercely.
Another objective of the invention is to provide an HMD capable of adjusting the positions of the image display unit portions easily, accurately and quickly according to the distance between the eyes for each player.
A further objective of the invention is to provide an HMD also capable of adjusting the angle formed by the optical axes of the image display unit portions, which correspond with the lines of sight of a player.
Another further objective of the invention is to provide an image display system capable of quickly forming appropriate three-dimensional images, wide images, or combined images of these two kinds in accordance with the content or type of images by using the above-described HMD.
A further objective of the invention is to provide an HMD which is sanitary even if it is used by many and unspecified players.
A further objective of the invention is to provide an HMD which easily enables model changes.